1. Field of the Invention
The disclosed and claimed concept relates to a network transformer primary disconnect assembly and, more particularly to an interlock assembly for a network transformer primary disconnect assembly.
2. Background Information
A network transformer is, typically, paired with both a primary medium voltage disconnect and a low voltage network protector. These systems are commonly located below ground level and must be submersible. Upstream of the network transformer and other components located below ground level, i.e. On the line side of the circuit, is a medium voltage distribution switchgear. Typically, the primary medium voltage disconnect is not capable of withstanding fault currents. Thus, there is a need for a primary medium voltage disconnect that can withstand faults and interrupt rated load as well as fault load. The need to obtain the fault withstand, and load interrupting ratings, can be addressed by including an available medium voltage vacuum circuit breaker in the submersible enclosure. This solution, however, creates additional needs.
In this configuration, the primary medium voltage disconnect must be structured to be coupled to either the medium voltage vacuum circuit breaker or a ground conductor assembly. That is, when the network transformer is in operation, the primary medium voltage disconnect must be coupled to, and in electrical communication with, the medium voltage vacuum circuit breaker which is further coupled to, and in electrical communication with the network transformer. During maintenance, however, the primary medium voltage disconnect must be grounded so as to ground the upstream medium voltage distribution switchgear. An interlock assembly is needed to ensure that the primary medium voltage disconnect cannot be coupled to both the medium voltage vacuum circuit breaker and the ground conductor assembly at the same time.
Further, so that maintenance workers can quickly determine if the primary medium voltage disconnect is in a safe condition, the submersible housing assembly needs to be able to reveal the configuration of the primary medium voltage disconnect.